The use of radars in industrial and automotive applications is evolving rapidly. Radars are used in many applications to detect target objects such as airplanes, military targets, vehicles, and pedestrians. Radar finds use in number of applications associated with a vehicle such as collision warning, blind spot warning, lane change assist, parking assist and rear collision warning Pulse radar and FMCW (Frequency Modulation Continuous Wave) radar are predominately used in such applications.
In a radar system, a local oscillator generates a transmit signal. The transmit signal is amplified and transmitted by one or more transmit units. In an FMCW radar, a frequency of the transmit signal is varied linearly with time. For example, the frequency of the transmit signal increases at a constant rate from 77 GHz to 810 Hz in 100 micro-seconds. This transmit signal is referred as a ramp signal or a chirp signal. An obstacle scatters the transmit signal. The scattered signal is received by one or more receive units in the radar system.
A signal obtained by mixing the transmitted signal and the received scattered signal is termed as a beat signal. The beat signal is sampled by an analog to digital converter (ADC) and processed by a digital signal processor to estimate a distance and a velocity of the obstacle. The frequency of the beat signal is proportional to the range (distance) of the obstacle. For a moving obstacle, a phase of the beat signal varies across multiple ramp signals transmitted by the radar system. The frequency and phase of the beat signal from one or more receive units are analyzed by the digital signal processor to estimate the position and the velocity of the obstacle.
The transmit signal from the local oscillator is provided to the one or more transmit units, and the one or more receiver units, which may be on one or multiple chips and/or semiconductor devices. The one or more transmit or receive units may be located at different distances from the local oscillator which induces different routing delays in the transmit signal from the local oscillator to each transmit or receive unit. Also, the phase of the transmit signal received from the local oscillator at the one or more transmit units or receive units may differ. This causes errors in position and velocity estimation of the obstacle. A radar system with the local oscillator, the one or more transmit units and the one or more receive units on a single chip has a high power consumption, a high heat dissipation and also requires a large area.